Fuel efficiency in an automobile may be enhanced by shutting off the gasoline engine during brief periods of time when power from the engine is not required for propulsion, such as when the automobile is coasting or temporarily stopped at an intersection. However, the compressor of a traditional air conditioning system runs off the crankshaft of the gasoline engine, and therefore, the engine continues to operate during those inefficient periods to provide cooling comfort for the passengers of the automobile.
U.S. Pat. No. 7,156,156, issued to Haller et al. on Jan. 2, 2007 (hereinafter referred to as Haller '156), provides one solution to the problem of the air conditioning system not functioning when the engine is not running. The Haller '156 patent shows an evaporator having a refrigerant flowing there-through for transferring heat from a flow of air to the refrigerant in a first operating mode with the engine of the automobile running. The evaporator includes a manifold extending in a horizontal direction. At least one tube is in fluid communication with manifold and extends downward in a vertical direction away from the manifold.
The evaporator defines at least one cavity, or tank, for storing a phase change material (PCM) to transfer heat from the PCM to the refrigerant to cool and freeze the PCM in the first operating mode with the engine of the automobile running. The cavities of the Haller '156 patent are disposed adjacent to and engaging the plurality of tubes. In a second operating mode with the engine of the automobile dormant, heat is transferred directly from the flow of air to the PCM in the cavities to cool the flow of air and to melt or warm the PCM.
There remains a continuing need for improved evaporators having a PCM to increase the efficiency of air conditioning systems that continue to operate during brief periods of time when the engine of the automobile is shut off to increase the fuel efficiency of the automobile.